1. Field of the Invention
The invention relates to the field of combustion technology. It is concerned with a burner of the double cone type which is known, for example, from the publication EP 0,321,809 B1.
2. Description of Background
EP 0,321,809 B1 describes the basic design of a premixing burner of the double cone type. This burner essentially consists of at least two hollow part-cone bodies supplementing one another to form a body, with tangential air inlet slits and feeds for gaseous and liquid fuels, in which burner the center axes of the hollow part-cone bodies have a taper widening in the direction of flow and run so as to be offset relative to one another in the longitudinal direction. A fuel nozzle is placed on the burner head in the conical interior formed by the part-cone bodies. The gaseous fuel is fed to the combustion air stream, before it flows into the burner interior, via gas injectors arranged along the inlet slits. The formation of the fuel/air mixture thus takes place directly at the end of the tangential air inlet slits.
The premixing burner has, on the combustion space side, a front plate which serves as an anchorage for the part-cone bodies.
Like many other components of thermal machines, the burner of the double cone type also has high thermal stresses as a result of being subjected to media at widely varying temperatures.
Thus, widely differing thermal stresses occur in this premixing burner due to the fact that the outer parts of the part-cone bodies have lower temperatures than the inner parts, since the outer parts are subjected to radiation to a less pronounced extent and are cooled to a greater extent by the inflowing air and by the cold gaseous fuel fed in the same region via ducts. This gives rise, above all, to different thermal expansions of the part-cone bodies and of the gas feed ducts connected to them, said expansions exerting a load cyclically on, above all, the front plate connecting them, this having the adverse effect of causing fatigue cracks, thus reducing the life of the burner.
This thermal stress is system-induced and, in terms of the differential thermal expansions in the direction of the burner axis, can be changed only to an inadequate extent.